Clusters of underwater seismic sources

ABSTRACT

A submersible sound system may include a housing, an end piece, an elastic membrane, an end cap affixed to the elastic membrane, and a subwoofer speaker system disposed within the housing and supported by a speaker support. A bubble sound source may be defined by the speaker support, the speaker diaphragm, an anterior end of the housing, the elastic membrane, and the end cap. The housing, end piece, and a posterior surface of the speaker support may form a sealed enclosure. The sound system may include a tuning pipe disposed between the sealed enclosure and the bubble sound source. A Helmholtz resonator may be disposed anteriorly of the speaker system. Multiple sound system may be assembled to form a cluster. The cluster may be defined by the vertices of regular polyhedron. The sound systems may be controlled to maintain the speaker systems within acceptable thermal limits.

BACKGROUND

The subject matter described in the present disclosure was developedwith U.S. Low frequency acoustic and seismo-acoustic projectors findapplications in marine seismic survey, underwater, ocean acoustictomography, long-range acoustic navigation and communications. All theseapplications need powerful and efficient sound sources in a lowfrequency range such as frequency range 5-100 Hz.

The low frequency source can be one of various impulse types such asexplosive (e.g. dynamite), air-guns, plasma (sparker) sources andboomers, or marine vibrators (vibroseis) providing continuous frequencysweeps. Seismic air-gun surveys such as those used in the exploration ofoil and gas deposits underneath the ocean floor, produce loud, sharpimpulses that propagate over large areas and increase noise levelssubstantially. While air-guns conventionally are traditional tools toimage formations, structures, and deposits deep in the ocean substrate,they also have drawbacks from an engineering/industry point of view.They produce high power non-coherent sound pulses and often radiate indirections other than those required for hydrocarbon exploration. Also,their signal is not highly controllable, either in frequencies contentor stability. Marine Vibrators are a coherent type of sound source,which can be a quieter and less harmful technology. In addition, such asound source provides clearer, more precise and higher resolutionimaging of the bottom properties due to their coherent signal andstreamer array processing. Reducing and managing the impact of oilexploration on marine mammals may be important to oil and gas producers.Application of quiet and highly coherent marine vibrators as areplacement for the traditional air-gun technology has been anincreasing focus of oil and gas producers.

Current continuous wave type sources make use of hydraulic, pneumatic,piezoelectric or magnetostrictive drivers and different types ofresonance systems to store acoustic energy and to improve impedancematching, when generating low-frequency sound waves in water. The poweroutput of a simple acoustic source is proportional to the squares ofvolume, velocity, and frequency and needs a large vibrating area toachieve reasonable levels. As a result, the sound source can becomeunacceptably large and expensive.

Seismic sources in the form of an underwater gas-filled balloon (orbubble) have been proposed and patented, for example in U.S. Pat. Nos.10,139,503, 9,383,463, 8,634,276, 8,441,892, 8,331,198, the entiredisclosures of which are hereby incorporated by reference herein. Aresonant bubble seismic source is a simple, efficient, narrow-bandprojector. Seismic survey applications may demand a large frequency bandand underwater bubble sources may be mechanically tuned over a largefrequency band. In one system, a projector changes its resonancefrequency by mechanically changing a length of an air-duct between twoinside resonators. This tunable bubble seismic source is functional, butturbulent losses require large dimensions for the tunable air duct andfor the whole resonator. Furthermore, tunable resonance systems (e.g.,high-Q tunable systems) may have many other disadvantages. For example:they may be too sensitive to towing depth and water flow fluctuations;they may have limitations on their frequency sweep rate; they maytransmit only specific waveforms with a slowly changing frequency; theymay need a special resonant frequency control system to keep theresonant frequency equal to the instantaneous frequency of a transmittedsignal; and they may have a large start/stop transient time.

U.S. Pat. Nos. 10,139,503, 9,383,463, respectively, describe a broadbanddual bubble resonant system and a bubble resonator excited by aninternal motor driven pistons or by valve controlled air flow from ablower. Both systems may be relatively inefficient and expensive; theymay use a very complicated nonlinear motor control, either bycontrolling the motor itself or valves for the blower system. However,such systems may make it difficult to achieve high quality linear soundreproduction. An additional problem may be the noise caused by motoritself. Without special silencers, shock-mounts, and sound isolationfrom water, the motor noise radiates directly into the water and maycause additional problems for sound receivers with high sensitivity.

Therefore, it appears that an improved underwater sound source havinglow frequency transmission capabilities would be desirable for marineseismic surveying.

SUMMARY

In one aspect, a sound source may include a few gas filled underwaterair-resonators, at least one resonator in a form of cylindrical orspherical gas-filled bubble covered by an elastic membrane, separatinggas from water, and at least one subwoofer speaker, moving between theresonators and exciting oscillations of the gas pressure. The resonatorsand subwoofer may be permanently tuned to different frequencies,uniformly covering the working range of the frequencies. The subwoofermay be driven by an audio amplifier, amplifying the signal fromdigital-analog converter of the computer. The computer is connected tosensors associated with the subwoofer, measuring current, voltage,temperature and the position of the subwoofer cone. The computer may beprogrammed to equalize the impedance of the subwoofer and keep thetemperature and excursion of the subwoofer within safe limits.

In some aspects, the underwater subwoofers may be mounted on a frame ina polyhedral cluster, thereby achieving a very large power and highefficiency. The frame with a polyhedral structure may include suppressorfins and keels to make it stable when towed at a high speed.

In various aspects, a submersible sound system comprises: a housing; ahousing end piece in mechanical communication with a posterior end ofthe housing; an elastic membrane in mechanical communication with ananterior end of the housing; an end cap in mechanical communication withthe elastic membrane; and a subwoofer speaker system disposed within thehousing. The subwoofer speaker system comprises: a magnet assemblydisposed within the posterior end of the housing; a frame in mechanicalcommunication with the magnet assembly; a voice coil; a diaphragm inmechanical communication with the frame and configured to be driven bythe voice coil; a spider or damper to be used as the rear suspensionelement for a voice coil; a subwoofer speaker support in mechanicalcommunication with the frame; and an interior portion of the housing. Ananterior surface of the subwoofer speaker support, an anterior surfaceof the diaphragm, the anterior end of the housing, the elastic membrane,and the end cap together define a sealed cylindrical bubble soundsource.

In other aspects, a submersible sound system comprises: housing; ahousing end piece in mechanical communication with a posterior end ofthe housing; an elastic membrane in mechanical communication with ananterior end of the housing; an end cap in mechanical communication withthe elastic membrane; a resonator end wall in mechanical communicationwith the anterior end of the housing; a Helmholtz resonator throatdisposed within the resonator end wall; and a subwoofer speaker systemdisposed within the housing. The subwoofer speaker system comprises: amagnet assembly disposed within the posterior end of the housing; aframe in mechanical communication with the magnet assembly; a voicecoil; a diaphragm in mechanical communication with the frame andconfigured to be driven by the voice coil; a subwoofer speaker supportin mechanical communication with the frame and an interior portion ofthe housing; and a tuning pipe disposed within the subwoofer speakersupport. The housing, the housing end piece, and a posterior surface ofthe subwoofer speaker support together form a posterior enclosure. Ananterior surface of the resonator end wall, the anterior end of thehousing, the elastic membrane, and the end cap together define a sealedcylindrical bubble sound source. The anterior surface of the diaphragm,an anterior surface of the subwoofer speaker support, an anteriorportion of the housing, the resonator end wall, and the Helmholtzresonator throat together define a Helmholtz resonator. The Helmholtzresonator throat is configured to permit fluidic communication betweenthe Helmholtz resonator and the cylindrical bubble sound source. Thetuning pipe extends between the posterior enclosure and the Helmholtzresonator and is configured to permit fluidic communication between theposterior enclosure and the Helmholtz resonator.

In yet other aspects, an underwater sound system comprises a soundsystem support having a plurality of vertices and a plurality of soundsources. The plurality of vertices form the vertices of a regularpolyhedron. The plurality of sound sources in the vertices areequidistant from one center of the polyhedron, which is referred to as aphase center. Each of the plurality of sound sources comprise: ahousing; a housing end piece in mechanical communication with aposterior end of the housing; an elastic membrane in mechanicalcommunication with the anterior end of the housing; an end cap inmechanical communication with the elastic membrane; and a subwooferspeaker system disposed within the housing. The subwoofer speaker systemcomprises a magnet assembly disposed within the posterior end of thehousing; a frame in mechanical communication with the magnet assembly; avoice coil; a diaphragm in mechanical communication with the frame andconfigured to be driven by the voice coil; and a subwoofer speakersupport in mechanical communication with the frame and an interiorportion of the housing. An anterior surface of the subwoofer speakersupport, an anterior surface of the diaphragm, the anterior end of thehousing, the elastic membrane, and the end cap together define a sealedcylindrical bubble sound source. Each one of the plurality of soundsources is affixed to each one of the plurality of sound system supportvertices.

FIGURES

Various features of the embodiments described herein are set forth withparticularity in the appended claims. The various embodiments, however,both as to organization and methods of operation, together withadvantages thereof, may be understood in accordance with the followingdescription taken in conjunction with the accompanying drawings asfollows.

FIG. 1 is a diagram of one aspect of a submersible sound systemcomprising a subwoofer speaker system according to the presentdisclosure.

FIG. 2 depicts an equivalent electrical circuit for the submersiblesound system of FIG. 1 according to the present disclosure.

FIG. 3 is a frequency versus sound pressure plot for the response of thesubmersible sound system of FIG. 1 according to the present disclosure.

FIG. 4 is a diagram of one aspect of a submersible sound systemcomprising a subwoofer speaker system and a tuning pipe according to thepresent disclosure.

FIG. 5 depicts an equivalent electrical circuit for the submersiblesound system of FIG. 4 according to the present disclosure.

FIG. 6 is a frequency versus sound pressure plot for the response of thesubmersible sound system of FIG. 4 according to the present disclosure.

FIG. 7 is a diagram of one aspect of a submersible sound systemcomprising a dual opposing subwoofer speaker system according to thepresent disclosure.

FIG. 8 is a diagram of one aspect of a dual bubble submersible soundsystem comprising subwoofer speaker system according to the presentdisclosure.

FIG. 9 is a frequency versus sound pressure plot for the response of thedual bubble submersible sound system of FIG. 8 according to the presentdisclosure.

FIG. 10 is a diagram of one aspect of a submersible sound systemcomprising a subwoofer speaker system having a magnet assembly heat sinkaccording to the present disclosure.

FIG. 11 is a diagram of one aspect of a submersible sound systemcomprising a subwoofer speaker system having an anterior place Helmholtzresonator according to the present disclosure.

FIG. 12 depicts an equivalent electrical circuit for the submersiblesound system of FIG. 11 according to the present disclosure.

FIG. 13 is a frequency versus sound pressure plot for the response ofthe submersible sound system of FIG. 12 according to the presentdisclosure.

FIG. 14 is a frequency versus sound pressure plot comparing thefrequency outputs of the aspects of the submersible sound systemsdepicted in FIGS. 1, 4, and 11 according to the present disclosure.

FIG. 15 depicts an aspect of the submersible sound system of FIG. 11including a sound system control system according to the presentdisclosure.

FIG. 16 illustrates an aspect of a submersible sound system according tothe present disclosure

FIG. 17 depicts an aspect of an underwater sound system comprising acluster of sound sources each having a subwoofer speaker systemaccording to the present disclosure.

FIG. 18 depicts a variety of regular polyhedra defining positions of thesound sources disposed about the underwater sound system depicted inFIG. 18 according to the present disclosure.

DETAILED DESCRIPTION

There is a growing interest for a very low frequency sound source in thefrequency range below 100 Hz for such applications as Arctic under-iceacoustic, far-range navigation, communications and thermometry,sub-bottom seismic survey, et cetera. The ultra-low frequency soundpropagates without attenuation and loss of coherency at a very fardistance covering the water column from the surface to the ocean floor.Another benefit, which has been in an increasing focus of major oil andgas producers, is reducing the impact of noise from traditional air-gunson marine mammals.

A coherent sound source can advantageously be quieter and more benign tomarine mammals. Marine Vibrators are a coherent type of seismic source,which are less harmful for marine inhabitants. They also provide aclearer, more precise and higher resolution imaging of the bottomformations, structures, and deposits. To build a sound source with afrequency below 100 Hz is a hard task due to a very large emitted volumevelocity or product of aperture area relative to its lineardisplacement. For sound pressure levels (SPLs) larger than 200 dB re 1μPa at 1 meter, the volume displacement at 5 Hz cycle can be tens ofliters. Accordingly, systems with rigid or flexural vibrating diaphragmwith a large aperture area are difficult to build. Also, they areusually not efficient or have a very narrow bandwidth. Highly efficientfrequency sweeping sound sources on the base of tunable organ pipes showvery good performance for 150-2000 Hz frequency bandwidth.

However, a further decrease of the low frequency will be hard to achievebecause of the organ pipe growing dimension. The present disclosure mayaddress such giant design demands relative to underwater sound emittingby providing a coherent seismic marine sound source based on theapplication of an underwater, gas filled bubble resonator. The presentdisclosure provides a promising high power, highly efficient, andcoherent seismic source at low frequencies.

A gas-filled bubble offers a large radiating area and functions as agood impedance transformer with very high radiation efficiency. Theelastic membrane supports high volume displacement with a largeradiation aperture and prevents cavitation damage. Large volumedisplacement and velocity support the large radiation power. The soundsources have very small coupling effects in water and can work togetherin a large phased array. An infra-sound transducer with a resonator inthe form of an underwater bubble or balloon made from an elasticmaterial generates seismic waves in a different manner. However, thephysics of the dynamics is similar to the physics of air released froman air-gun.

The equation of the dynamics of spherical bubbles was first derived andused by Rayleigh (1917) and then Plesset (1949). The most general formof the equation of the dynamics with additional terms due to surfacetension and viscous effects in the bubble surface condition is widelyknown as the Rayleigh-Plesset equation. The practical bubble has a shapethat is different from spherical. Its internal pressure oscillations arecomparable with the difference of static gravity forces andacoustic-gravity oscillations and are part of its dynamics. The realQ-factor of a practical bubble may be smaller than a theoreticalQ-factor. The best transducer to excite the propagating spherical waveis a sphere. It may be desirable to have the shape of the seismic sourceas close as possible to the sphere. However, practically it may bedifficult to keep the spherical shape of the oscillating resonator inwater, especially if it is towed. The buoyant force will pool at the topof the large spherical bubble and deform it. In response, a reasonableengineering compromise can be a short horizontal cylinder. Such acylinder has cylindrical symmetry, can be towed, and can better retainits shape in the water. The bubble source, consisting of cylindricalsections, has been described in the U.S. Pat. Nos. 10,139,503,9,383,463, 8,634,276, and 8,441,892, the disclosures of which areincorporated by reference herein in their entirety and for all purposes.A simplified linear acoustic model of the bubble is based on a wavepropagation condition and an adiabatic equation for an underwater bubblestate.

The following Equations 1 through 6 are derived from Newton, Hooke,adiabatic (Boyle-Mariotte) and Euler laws. The pressure p in a sphericalwave with the wave number k=ω/c at the distance r from the source isknown from a spherical symmetry and wave propagation exponent:

$\begin{matrix}{{p = \frac{\exp ( {{- i}{kr}} )}{r}},} & {{Equation}\mspace{14mu} 1}\end{matrix}$

where c is the sound, velocity f is the frequency; k=ω/c, ω=2πf in whichω is the angular frequency of the wave.

The Euler's equation gives the velocity of water particles u:

$\begin{matrix}{{u = {{{- \frac{1}{i\; \rho \; \omega}}\frac{\partial p}{\partial r}} = {\frac{( {{ikr} + 1} )}{i\; \omega \; \rho \; r}p}}},} & {{Equation}\mspace{14mu} 2}\end{matrix}$

where ρ_(w) is the water density. The combination of the above equationsgives the impedance Z_(b) of the bubble:

$\begin{matrix}{{Z_{b} = {\frac{p}{1} = {\frac{i\; \omega \; \rho_{w}{r_{b}/A_{b}}}{1 + {ikr}_{b}} = \frac{1}{\frac{1}{i\; \omega \; L_{b}} + \frac{1}{R_{b}}}}}},} & {{Equation}\mspace{14mu} 3}\end{matrix}$

where l=uA_(b) is the volume velocity; A_(b) is the aperture area; r_(b)is the radius of the cylinder; c_(w) is the sound velocity in water; and

$L_{b} = {{\frac{\rho_{w}r_{b}}{A_{b}}\text{;}\mspace{14mu} R_{b}} = \frac{\rho_{w}c_{w}}{A_{b}}}$

are equivalent parameters of the electrical model.

The Hooke law explains the stretching of the cylindrical membrane:

$\begin{matrix}{p = {{I\text{/}( {i\; \omega \; \frac{A_{b}r_{b}^{2}}{E_{m}h_{m}}} )} = {I\text{/}( {i\; \omega \; C_{m}} )}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

where E_(m) is the Young modulus of the membrane material; h_(m) is thethickness of the membrane;

$C_{m} = \frac{A_{b}r_{b}^{2}}{E_{m}h_{m}}$

is the equivalent capacitor of the electrical model.

The adiabatic oscillations of bubble gas have the pressure oscillationsdp:

$\begin{matrix}{{dp} = {\frac{{dvP}_{b}}{V_{b}\gamma} = {\frac{I}{i\; \omega \; \gamma \; V_{b}\text{/}P_{b}} = \frac{I}{i\; \omega \; C_{b}}}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Where γ=1.4 is the adiabatic constant and V_(b), P_(b), are theequilibrium volume and pressure of the bubble; C_(b)=V_(b)γ/P_(b), isthe equivalent capacitor of the electrical model.

Finally the air duct with the length l_(h), and area of the pipe A_(h),has the equation for its flow l=uA_(n), and pressure p:

$\begin{matrix}{p = {{i\; \omega \; \frac{\rho_{a}l_{h}}{A_{h}}I} = {i\; \omega \; L_{h}I}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

where ρ_(a) is the air density;

$L_{h} = \frac{\rho_{a}l_{h}}{A_{h}}$

and l is the inductance of the electrical model.

In a majority of cylindrical bubble systems, the sound source typicallyincludes a motor and a piston; or a powerful blower and valvescontrolled by the motor. Both of these approaches are limited in thefrequency range attainable. It is difficult to drive a piston with massM by a rotary motor with a crank shaft mechanism or linear motor. Theforce F on the piston can be calculated as F=M*a, where acceleration,a=d*(2*π*f)². For 100 Hz, the acceleration will be a=d*394784. For agiven displacement of 1 cm and piston mass 1 kg, the force will be 4000N. This very large force is not easy to achieve by simple mechanicalengineering solutions. However, a typical subwoofer system can readilywork at a frequency of 100 Hz. A standard commercial off-the-shelf(COTS) subwoofer may be fabricated of strong and light compositematerials, have neodymium magnets having large magnetic strength, andmay also include a cooling system. The use of a subwoofer speaker systemcan readily operate at 100 Hz. A typical audio speaker may have adynamic range between 20 Hz-20 kHz in air, and a typical woofer speakermay operate in a range between 20 Hz-2000 Hz range. However, thesubwoofer—using a matching impedance acoustical system includingcylindrical underwater air-bubble resonator as described herein—mayproduce a very loud sound underwater in a very low frequency rangebetween 10 Hz-200 Hz. The matching impedance acoustical system may referto matching speaker impedance of the subwoofer speaker system with theradiation impedance of the water surrounding the subwoofer system.

In some aspects, a subwoofer speaker system may have a diameter between12″-15″ and operate at root mean square (RMS) electric power up to 10 kWfor a frequency band between 10 to 200 Hz. A subwoofer may differ from atypical audio speaker in that the subwoofer may have a very largespeaker excursion of up to 2″, very strong motor force BI=20-30Tesla-meter, and may have a very low resonance frequency at aboutresonance 25 Hz-40 Hz. The traditional subwoofer may use aferrite-strontium magnet, while the more advanced subwoofers may useneodymium rare earth magnets with very high magnetic field.Additionally, the subwoofer frame can handle very high temperatures. Thesubwoofer cones may be built from aluminum or composite (carbon-fiber,Kevlar™) multilayer structures, which are light and very strong. Thesubwoofers can operate at very high power up to 10 kW and more at highefficiency.

For limited power applications (e.g., limited by 185 dB SPL re 1 μPa at1 m) the standard sub-woofer can be much easier, more practical andlower cost for an acoustical exciter. In some aspects, a subwoofer maybe available at the 1000-3000 kW RMS electric power range. Suchactuators are highly linear, easy to drive by a standard audioamplifier, and easy to install and to replace if needed. In addition, asubwoofer system controller can use information about voltage, current,excursion and heat to match impedance and keep the subwoofer in a safecondition. In aspects in which very high power (up to 230 dB SPL re 1μPa at 1 m) is desired, multiple underwater subwoofers may be mounted ona frame in a polyhedron cluster. In some aspects, the vertices orcorners of the polyhedron are equidistant from one phase center andoperate as one very efficient spherical wave underwater sound source.The frame with such a polyhedron structure may include suppressor finsand keels to make it stable when towed at a high speed. Such clusterscan be combined into array structures and create needed directivitypatterns.

It may thus be recognized that the use of one or more subwoofer systemsin an underwater sound source may provide a simplified acousticalactuator and control system, improve linearity and frequency response ofthe sound system, improve the reliability of the sound system, andsimplify maintenance issues, while operating at a frequency range notreadily achievable by other mechanical-based underwater sound systems.

The sub-woofer also can be represented by a simple model as illustratedby Equation 7:

$\begin{matrix}{p = {{I_{c}\frac{Bl}{A_{s}}} = {{{i\; {\omega ( \frac{M_{s}}{A_{s}^{2}} )}1} + \frac{I}{i\; {\omega ( {A_{s}^{2}C_{ms}} )}}} = {{i\; \omega \; L_{s}I} + \frac{I}{i\; \omega \; C_{s}}}}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

where C_(ms) is the mechanical compliance; M_(s) is the moving partsmass; Bl is the motor strength; A_(s) is the effective radiating area;

$L_{s} = \frac{M_{s}}{A_{s}^{2}}$

is the equivalent inductance and C_(s)=A_(s) ²C_(ms) is the equivalentinductance. Equation 8 is for the electrical part of the subwoofer andincludes back electromotive force (EMF) pAsBI, the inductance of thecoil L_(c) and resistance of the coil R_(c):

U−BlI/A_s=I _(c)(iωL _(c) +R _(c))  Equation 8:

where U is the voltage of the input signal; l_(c) is the current throughthe coil.

In the following aspects of submersible sound systems, the equivalentresonance structures are composed of combinations of the equivalentelectrical elements as disclosed above. Among the various aspectsdisclosed below, the transition from air to underwater sound propagationis the principal difference from the traditional audio engineeringsystems for air propagated sound. The simplest system with the smallestnumber of poles is a 4 pole system.

Basic Submersible Sound System with Subwoofer

FIG. 1 depicts a first aspect of a submersible sound system 100. Thebasic submersible sound system 100 includes a sealed chamber 110 at aposterior end and a cylindrical bubble source 120 at an anterior end.The sealed chamber 110 is composed of a cylindrical housing 112 to whicha housing end piece 114 is affixed at a posterior end of the cylindricalhousing 112. The cylindrical bubble source 120 is configured to befilled with gas. The cylindrical bubble source 120 is composed of acylindrical elastic polyurethane membrane 122 that is affixed at ananterior end of the cylindrical housing 112. The cylindrical bubblesource 120 also includes an end cap 124 that is sealed at the anteriorend of the elastic membrane 122. The elastic membrane 122 may separate asubwoofer driver (not illustrated) from the buoyancy forces of thesurrounding water and enable a speaker diaphragm 136 to be loadeduniformly. In some aspects, the end cap 124 may be a solid piece. Insome aspects, the end cap 124 may also include a deformable membrane.

Disposed within the submersible sound system 100 is a subwoofer speakersystem 130. In some aspects the subwoofer speaker system 130 is disposedwithin the posterior end of the housing 112. The subwoofer speakersystem 130 is composed of a magnet assembly 132, a frame 134, a voicecoil (not illustrated), and the speaker diaphragm 136. The frame 134 isconfigured to support the magnet assembly 132 and the speaker diaphragm136. The magnet assembly 132 is disposed within the sealed chamber 110at the posterior end of the submersible sound system 100. The subwooferspeaker system 130 is supported in the housing 110 by means of asubwoofer speaker support 138. The sealed chamber 110 is maintained in asealed configuration by means of the cylindrical housing 112, thehousing end piece 114, a posterior end of the subwoofer speaker support138, and a posterior surface of the diaphragm 136.

The speaker diaphragm 136 is driven by the voice coil in response toreceiving an AC electrical signal. The AC electrical signal may besourced by a control circuit that may control an amplitude and afrequency of the AC electrical signal. The magnetic field developedwithin the voice coil due to the AC electrical signal may cause thevoice coil and the diaphragm 136, to which it is attached, to moverelative to a static magnetic field produced by the magnet assembly 132.When the diaphragm 136 is actuated by the voice coil, its motionperturbs the gas disposed within the bubble source 120. In this way, thesubwoofer speaker system 130 radiates sound through the gas-filledbubble source 120 that includes the cylindrical elastic membrane 122. Itmay be understood that the bubble source 120 may also be maintained in asealed configuration defined by the end cap 124, the cylindrical elasticmembrane 122, an anterior surface of the subwoofer speaker support 138,and an anterior surface of the diaphragm 136.

It is recognized that a sealed enclosure can have a relatively smoothroll-off and flat response in an acoustical system. Equations 9 through12 relate to the response of the sound system 100 depicted in FIG. 1 andinclude:

$\begin{matrix}{\mspace{79mu} {{U - {{Bl}\; \frac{I}{A_{s}}}} = {I_{c}( {{i\; \omega \; L_{c}} + R_{c}} )}}} & {{Equation}\mspace{14mu} 9} \\{{I_{c}\frac{Bl}{A_{s}}} = {{{i\; \omega \; L_{s}I} + \frac{I}{i\; \omega \; C_{s}} + \frac{I}{i\; \omega \; C_{0}} + {{IZ}_{b}\text{;}\mspace{14mu} p_{b}}} = {{{IZ}_{b}\text{;}\mspace{14mu} p_{r}} = \frac{P_{b}}{{( {\frac{1}{i\; \omega \; L_{b}} + \frac{1}{R_{b}}} )\frac{1}{i\; \omega \; C_{m}}} + 1}}}} & {{Equation}\mspace{14mu} 10} \\{\mspace{79mu} {Z_{b} = \frac{1}{{i\; \omega \; C_{b}} + \frac{1}{\frac{1}{i\; \omega \; C_{m}} + \frac{1}{\frac{1}{i\; \omega \; L_{b}} + \frac{1}{R_{b}}}}}}} & {{Equation}\mspace{14mu} 11}\end{matrix}$

where V₀ is the volume of the resonator behind the subwoofer

$\begin{matrix}{C_{0} = {{P_{b}\gamma \text{/}V_{0}\text{;}\mspace{14mu} C_{b}} = {{P_{b}\gamma \text{/}V_{b}\text{;}\mspace{14mu} L_{s}} = {{\frac{M_{s}}{A_{s}^{2}}\text{;}\mspace{14mu} C_{s}} = {{A_{s}^{2}C_{ms}\text{;}\mspace{14mu} R_{b}} = {{\frac{\rho_{w}C_{w}}{A_{b}}\text{;}\mspace{14mu} C_{m}} = \frac{A_{b}r^{2}}{E_{m}h_{m}}}}}}}} & {{Equation}\mspace{14mu} 12}\end{matrix}$

FIG. 2 depicts an equivalent electrical circuit 200 for the response ofthe submersible sound system depicted in FIG. 1. Additional parameterspresented in the equivalent electrical circuit 200 includeR_(s)=ω_(r)L_(s)/Q_(s); R_(m)=4μ/(rA_(b)), where μ is the jointviscosity of water, Q_(s) is the mechanical Q-factor of the loudspeaker,and ω_(r)=2πf is the mechanical resonance frequency of the loudspeaker.The electrical circuit is connected to the acoustical equivalent circuitthrough a gyrator and in which the back EMF is defined byu=BlI_(s)/A_(s); p=BlI_(c) where l_(s) is the volume velocity throughthe speaker, p is the pressure on the speaker, I_(c) is the currentthrough the speaker coil, and A_(s) is the speaker cone area.

FIG. 3 depicts a simulation 300 of the frequency response of thesubmersible sound system depicted in FIG. 1 according to the equationsdisclosed above. Table 1 presents the parameters describing thesubwoofer speaker system. Table 2 presents the parameters describing theenclosure and the bubble. As can be observed in FIG. 3, the sound systemsupports good sound pressure at about 184 dB. The frequency response issmooth with a little dip in the center. The efficiency of the system isabout 1%.

TABLE 1 Subwoofer Diameter of the subwoofer 12″ Fs (air free resonance,Hz) 37.6 Qms (Q, mechanical) 3.705 Re (DC resistor, ohms) 1 Le(inductance, mH) 9.35 Xmax (one way linear excursion, mm) 47 RMS power,Watts 3000 Nominal power, Watts 6000 Mms (total moving mass, kg)0.501511 Cms (mechanical compliance, mm/N) 0.036 B1 (motor strength,Tesla M) 16.19 Sd (effective radiating area, sq. m)) 0.045239

TABLE 2 Enclosure Diameter of the cylindrical hull, inch 14 Length ofthe motor box, inch 14 Volume of the box, L 35 Length of the bubblemembrane, inch 10 Volume of the bubble, L 25 Area of the membrane, sq. m0.28 Hardness of the membrane, 70 A Thickness of the membrane, mm 3.17Water depth, m 6

Submersible Sound System with Vented Subwoofer

FIG. 4 depicts a second aspect of a submersible sound system having avented subwoofer driver that includes a tuning pipe. The tuning pipesubmersible sound system 400 includes a chamber 410 at a posterior endand a cylindrical bubble source 420 at an anterior end. The chamber 410is composed of a cylindrical housing 412 to which a housing end piece414 is affixed at a posterior end of the cylindrical housing 412. Thecylindrical bubble source 420 is configured to be filled with gas. Thecylindrical bubble source 420 is composed of a cylindrical elasticpolyurethane membrane 422 that is affixed at an anterior end of thecylindrical housing 412. The cylindrical bubble source 420 also includesan end cap 424 that is sealed at the anterior end of the elasticmembrane 422. The elastic membrane 422 may separate the subwoofer driverfrom the buoyancy forces of the surrounding water and enable a speakerdiaphragm 436 to be loaded uniformly. In some aspects, the end cap 424may be a solid piece. In some aspects, the end cap 424 may also includea deformable membrane.

Disposed within the vented submersible sound system 400 is a subwooferspeaker system 430. In some aspects, the subwoofer speaker system 460 isdisposed at a posterior end of the cylindrical housing 412. Thesubwoofer speaker system 430 is composed of a magnet assembly 432, aframe 434, a voice coil (not illustrated), and the speaker diaphragm436. The frame 434 is configured to support the magnet assembly 432 andthe speaker diaphragm 436. The magnet assembly 432 is disposed withinthe chamber 410 at the posterior end of the vented submersible soundsystem 400. The subwoofer speaker system 430 is supported in the housing410 by means of a subwoofer speaker support 438.

The speaker diaphragm 436 is driven by the voice coil in response toreceiving an AC electrical signal. The AC electrical signal may besourced by a control circuit that may control an amplitude and afrequency of the AC electrical signal. The magnetic field developedwithin the voice coil due to the AC electrical signal may cause thevoice coil and the diaphragm 436, to which it is attached, to moverelative to a static magnetic field produced by the magnet assembly 432.When the diaphragm 436 is actuated by the voice coil, its motionperturbs the gas disposed within the bubble source 420. Thus, the ventedsubmersible sound system 400 radiates sound into the surrounding waterthrough this perturbed gas and elastic membrane 422. It may beunderstood that the bubble source 420 may be maintained in a sealedconfiguration defined by the end cap 424, the cylindrical elasticmembrane 422, an anterior surface of the subwoofer speaker support 438,and an anterior surface of the diaphragm 436.

The vented submersible sound source may also include a tuning pipe 450to vent the chamber 410 to the bubble source 420. In some aspects, thetuning pipe 450 is disposed within the subwoofer speaker support andextends between the chamber 410 and the cylindrical bubble sound source420. The tuning pipe 450 may be configured to permit fluidiccommunication between the chamber 410 and the cylindrical bubble soundsource 420. In some aspects, the chamber 410 and the tuning pipe 450together comprise a Helmholtz resonator.

In operation, when the diaphragm 436 moves, its cone vibrates in bothdirections, forwards toward the bubble source 420, and backwards to thechamber 410 which is vented to the bubble source 420 by the tuning pipe450. The diaphragm 436 thus acts as a piston oscillating between twochambers. The tuning pipe 450 and chamber 410 together form a Helmholtzresonator having a resonance frequency below that of the bubble source420. The volume of chamber 410 acts like compliance and the air in thetuning pipe 450 acts as inertia. The resonance frequency of thisresonator is shown by Equation 13:

$\begin{matrix}{{f_{r} = {\frac{1}{2\; \pi \sqrt{LC}} = {\frac{1}{2\; \pi}\sqrt{\frac{{AP}\; \gamma}{\rho_{a}l\; V},{{{where}\mspace{14mu} L} = {{\frac{\rho_{a}l}{A}\text{;}\mspace{14mu} C} = \frac{V}{P\; \gamma}}}}}}},} & {{Equation}\mspace{14mu} 13}\end{matrix}$

where L=ρ_(a)l/A is inertia of the air with the density p_(a) in a pipewith the length l and cross section area A; C=V/Pγ is the compliance ofair in the volume V and pressure P behind the subwoofer. This formulashows how resonance frequency related to pipe length and cross sectionarea.

When cone of the diaphragm 436 moves inside the chamber 410 it shrinksthe air volume and increases the pressure within the chamber 410. Thispressure moves air through the tuning pipe 450. When air moves out thechamber 410, the internal pressure drops and air start moving back in.The air in the chamber 410 thus oscillates like a mass (air inside pipe)with a spring (the air inside of the tuning pipe 450). When thefrequency of the diaphragm 436 oscillates at the same frequency as thefrequency of the chamber resonance, the velocity of air in the tuningpipe 450 reaches a maximum. At frequencies above the resonance frequencyof the chamber 410, the air flow from tuning pipe 450 to the bubblesource 420 will be in phase with the diaphragm motion. As such, theresonance of the underwater bubble source 420 is designed so that thespeaker impedance matches the radiation impedance of the surroundingwater.

FIG. 5 presents an equivalent electrical circuit 500 for the frequencyresponse of the vented subwoofer system 400. The chamber 410 forms avery low frequency Helmholtz resonator with the equivalent capacitorC₀=P_(b)γ/V₀ and inductor

${L_{0} = \frac{\rho_{a}l_{0}}{A_{0}}},$

where A₀, I₀ are the cross-area and length of the port.

${R_{0} = \frac{\omega_{r}L_{0}}{Q_{0}}},$

Q_(s) is the Q-Factor of the Helmholtz port; ω_(r)=2πf_(r) is theresonance frequency of the Helmholtz port. The full set of equations isnot very different to that presented for the aspect of the sound systemdepicted in FIG. 1 and as disclosed above.

TABLE 3 Enclosure Diameter of the cylindrical hull, inch 14 Length ofthe motor box, inch 14 Volume of the box, L 35 Length of the bubblemembrane, inch 10 Volume of the bubble, L 25 Area of the membrane, sq. m0.28 Hardness of the membrane, 70 A Thickness of the membrane, mm 3.17Length of the box port pipe, inch 14 Diameter of port, inch 1 Waterdepth, m 6

Table 3 presents parameters of the vented enclosure (comprising chamber410 and tuning pipe 450) used in a frequency response simulation of thevented submersible sound system depicted in FIG. 4. The parameters ofTable 3 are the same as in the submersible sound system depicted in FIG.1 with the addition of parameters related to the tuning pipe 450.

FIG. 6 depicts the frequency response curve 600 for the simulation ofthe output of the vented submersible sound system 400. The parametersrelated to the enclosure are those listed in Table 3, while theparameters of the subwoofer are the same as in Table 1.

It may be observed that the addition of the tuning pipe 450 to thechamber 410 may result in a lowering of the lower-end boundary of thefrequency response curve 600 to about 12 Hz, 10 Hz, or even to about 5Hz. However, the SPL of the sound signal may decrease at the center ofthe frequency band which may be due to the added dimension of the tuningpipe 450. Sealed ports easily permit pressure compensation when thesubmersible sound system is actively submerging to lower depths in thewater The submersible vented subwoofer sound system may effectively actas a sealed enclosure for a tuning pipe 450 having a very smalldiameter.

Water-Cooled Dual Subwoofer System

FIG. 7 depicts yet another aspect of a submersible subwoofer soundsystem. Depicted in FIG. 7 is a water-cooled dual subwoofer sound system700. The dual subwoofer system 700 includes many of the features of thebasic subwoofer system 100 as depicted in FIG. 1 and disclosed above.Thus, the submersible sound system 100 includes a sealed chamber 710 ata posterior end and a cylindrical bubble source 720 at an anterior end.The sealed chamber 710 is composed of a cylindrical housing to which ahousing end piece is affixed at a posterior end of the cylindricalhousing. The cylindrical bubble source 720 is configured to be filledwith gas. The cylindrical bubble source 720 is composed of a cylindricalelastic polyurethane membrane that is affixed at an anterior end of thecylindrical housing. The cylindrical bubble source 720 also includes anend cap that is sealed at the anterior end of the elastic membrane. Theelastic membrane may separate the subwoofer driver from the buoyancyforces of the surrounding water and enable a speaker diaphragm to beloaded uniformly. In some aspects, the end cap may be a solid piece. Insome aspects, the end cap may also include a deformable membrane.

A distinction between the basic submersible sound system 100 and thedual subwoofer submersible sound system 700 is that the dual subwoofersubmersible sound system 700 includes a pair of subwoofer speakersystems 730 a,b. Each of the pair of subwoofer speaker systems 730 a,bmay be disposed within a posterior end of the cylindrical housing. Eachof the pair of the subwoofer speaker systems 730 a,b includes a magnetassembly, a frame, a voice coil, and the speaker diaphragm. Each frameis configured to support the magnet assembly and the speaker diaphragmof the respective subwoofer speaker system 730 a,b. As may be determinedin FIG. 7, a first subwoofer speaker system 730 a has a magnet assemblydisposed within the sealed chamber 710 while the diaphragm, facing theanterior portion of the sound system 700, is acoustically coupled to thecylindrical bubble source 720. The second subwoofer speaker system 730 bhas a magnet assembly also disposed within the sealed chamber 710 whilethe diaphragm, facing the posterior portion of the sound system 700, isacoustically coupled to the sealed chamber 710. Each of the subwooferspeaker systems 730 a,b is supported in the housing 710 by means of arespective subwoofer speaker support 738 a,b.

The speaker diaphragm of each of the two subwoofer speaker systems 730a,b is driven by the voice coil in response to receiving an ACelectrical signal. The AC electrical signal may be sourced by a controlcircuit that may control an amplitude and a frequency of the ACelectrical signal. In some aspects, the diaphragm of the first subwooferspeaker system 730 a may be driven in an opposing phase to the diaphragmof the second subwoofer speaker system 730 b.

The housing of the dual underwater subwoofer system may be fabricatedfrom material with a high thermal conductivity, to cool air inside thesound system 700. In one non-limiting example, the housing may befabricated out of aluminum 6061 T6. In use, the underwater subwoofer 700is typically surrounded by water 780. As disclosed above, the twosubwoofer sound systems 730 a,b may operate in an isobaric push-pullmode, in which the diaphragms both move together in a single direction(either anterior or posterior) thereby keeping a constant volume betweencones. To maintain the volume, air may be displaced through a sealedchannel 740 and a central path 782 that is in thermal communication withthe exterior water 780. Because the magnets and sealed channel 740 aresurrounded by water 780 their temperature cannot exceed 100 degrees C.The housing having a high temperature conductively can also essentiallycool the gas inside.

Each subwoofer speaker system 730 a,b may be driven only by half of thecurrent or a quarter of the power of a single subwoofer system sounddevice. As a result, each subwoofer speaker system 730 a,b produces onlya quarter of the temperature of a single subwoofer device. As a result,each subwoofer speaker system 730 a,b of the dual subwoofer sound source700 will not suffer as much thermal degradation as the single subwooferspeaker driven at its maximum power. Therefore, each subwoofer speakersystem 730 a,b will be able to operate for a longer time and at agreater power compared to the single subwoofer speaker system.

Dual-Resonance Dual-Aperture Subwoofer System

A dual resonance dual aperture system is depicted in FIG. 8. The dualresonance subwoofer system 800 is similar to the basic subwoofer system100 as depicted in FIG. 1 and disclosed above, except the dual resonancesubwoofer system 800 also includes a second bubble source 810 at theposterior end. Many of the features of the dual resonance system 800 aresimilar to those found in the basic subwoofer system 100.

The dual resonance sound system 800 includes a first cylindrical bubblesource 820 at an anterior end and a second cylindrical bubble source 810at a posterior end. The first cylindrical bubble source 820 is composedof a first cylindrical elastic polyurethane membrane 822 a that isaffixed at an anterior end of a cylindrical housing 812. The firstcylindrical bubble source 820 also includes an end cap 824 that issealed at the anterior end of the first elastic membrane 822 a. In someaspects, the end cap 824 may be a solid piece. In some aspects, the endcap 824 may also include a deformable membrane. The second cylindricalbubble source 810 is composed of a second cylindrical elasticpolyurethane membrane 822 b that is affixed at a posterior end of acylindrical housing 812. The second cylindrical bubble source 810 alsoincludes an endpiece 814 that is sealed at a posterior end of the secondelastic membrane 822 a-b. In some aspects, the endpiece 814 may be asolid piece. In some aspects, the endpiece 814 may also include adeformable membrane. Both of the first cylindrical bubble source 820 andthe second cylindrical bubble source 810 are configured to be filledwith gas. In some aspects, an acoustic resonance of the firstcylindrical bubble source 810 may differ from the acoustic resonance ofthe second cylindrical bubble source 820. In some aspects, an acousticresonance of the first cylindrical bubble source 810 may be the same asthe acoustic resonance of the second cylindrical bubble source 820.

Disposed within the submersible sound system 100 is a subwoofer speakersystem 830. In some aspects, the subwoofer speaker system 830 isdisposed at a posterior end of the cylindrical housing 812. Thesubwoofer speaker system 830 is composed of a magnet assembly, a frame,a voice coil (not illustrated), and a speaker diaphragm 836. The frameis configured to support the magnet assembly and the speaker diaphragm836. The magnet assembly is disposed within the cylindrical housing 812.The subwoofer speaker system 830 is supported in the housing 812 bymeans of a subwoofer speaker support. It may be understood that thesecond bubble source 8100 may also be maintained in a sealedconfiguration defined by the end cap 814, the second cylindrical elasticmembrane 822 b, a posterior surface of the subwoofer speaker support838, and a posterior surface of the diaphragm 836. The elastic membranes822 a-b may respectively separate the driver vibrating the speakerdiaphragm 836 from the buoyancy forces of the surrounding water andenable the speaker diaphragm 836 to be loaded uniformly.

The speaker diaphragm 836 is driven by the voice coil in response toreceiving an AC electrical signal. The AC electrical signal may besourced by a control circuit that may control an amplitude and afrequency of the AC electrical signal. The magnetic field developedwithin the voice coil due to the AC electrical signal may cause thevoice coil and the diaphragm 836, to which the voice coil is attached,to move relative to a static magnetic field produced by the magnetassembly. When the diaphragm 836 is actuated by the voice coil, itsmotion perturbs the gas disposed within the first bubble source 820 andthe second bubble source 810.

The system has two close resonances and shows a very high efficiency.The system consists from two bubble resonators 810, 820 excited by onesubwoofer speaker 830. The second bubble resonator 810 may have largervolume and hence the lower resonance frequency than the first bubbleresonator 820. By changing the length of rigid support tubing betweenthe two cylindrical bubble resonators 820, 810, the low resonancefrequency can be shifted and moved close to the high resonancefrequency. By doing so, the submersible system may have a narrow outputband and be extremely efficient. The dual resonance dual apertureunderwater subwoofer is very suitable in applications in which a largebandwidth output is unnecessary, but high sound pressure levels aredesired. However, the dual resonance structure of the frequency responsemakes the frequency bandwidth large enough for applications such as longrange underwater positioning and ocean acoustic tomography.

FIG. 9 shows a power versus frequency graph 900 for a simulation of thedual resonance sound system 800. The simulation parameters of thesubwoofer are the same as in the previous variants and shown in Table 1.Each bubble source (820 and 810 of FIG. 8) has a diameter 14″ and alength of 10″. A rigid aluminum tubing support structure (not shown) ofthe elastic membranes 822 a,b is also 10″ in length. As can be observedin the graph 900, this sound source shows very high signal in the lowfrequency band from 14 to 24 Hz. It shows very high efficiency 10% andhigh SPL (>190 dB) in this narrow frequency band. The band can beexpanded if a subwoofer having a heavy aluminum diaphragm with a verylow frequency resonance is used.

The two resonators of the dual resonance sound system 800 are connectedthrough a subwoofer driver. As shown in FIG. 8, the subwoofer system 800has two sides and it operates similarly to a piston. When thesubwoofer/speaker cone is moving to the right, this movement maycompress air in the right side or chamber and expand air behind the conein the left side or chamber. Conversely, when the cone moves back suchas back to the left, this compresses air behind the speaker and expandsair in the right side. In this way, when the subwoofer is placed in thehole of the wall between the two bubble resonators, the subwoofer canexcite both of the resonators simultaneously or substantiallysimultaneously, but in opposing directions.

The two bubble resonators may be tuned to two different frequencies, F₁and F₂. They may have the same membrane dimensions and have differentbubble volumes, as shown in the FIG. 16. Generally, however, both bubbleresonators may have different volumes and different areas of theirmembranes. The resonance frequency f_(r) of the bubble resonator isdefined by Equation 14:

$\begin{matrix}{f_{r} = {\frac{1}{2\; \pi}\sqrt{\frac{{AP}\; \gamma}{\rho_{a}{RV}}}}} & {{Equation}\mspace{14mu} 14}\end{matrix}$

Different volumes of the resonators allow them to be tuned to twodifferent frequencies in conjunction with setting their resonances closeto each other. Such a dual-resonance system will beneficially have anexpanded frequency band while remaining very powerful and efficient. Fortypical resonance frequency and phase responses, the dual-resonancesystem may generate a radiated signal of the same phase relative to thetwo resonators. The radiated signal may generated so that speakerimpedance of the dual resonance sound system 800 matches the radiationimpedance of water. Because the speaker cone is moving between the tworesonators, the cone shrinks one volume and expands another at the sametime. In other words, the cone excites the resonators in oppositephases. But oscillations higher than the resonance frequency will beshifted in phase counterclockwise while oscillations lower than theresonance frequency will be shifted in phase 90 degrees clockwise. Asresult, between resonances, the radiated signal will be in one phasefrom both resonators so the double resonance sound system 800 willradiate very well. As described above, the elastic membranes 822 a,b maybe flexible members. On the other hand, the end cap 814 can be rigid andnot moving. The cylindrical housing of the two cylindrical bubbleresonators 820, 810 also can be rigid or fixed and not moving.

The volume behind the speaker is compressing even when the speaker conemoves but is not radiating a signal. As discussed herein, the tuningpipe may vent the subwoofer enclosure to act as phase invertor so thatmotion is inverted back and used in the main bubble resonator.Alternatively, the chamber behind the speaker also has a bubbleradiating to the water using the back-and-forth motion of the cone(e.g., as the cone moves back) for the radiation. This way, sound wavesare radiated by the two bubbles, in which each bubble uses the samespeaker cone moving between the two bubbles.

Underwater Subwoofer Sound System with Heat Sinks

FIG. 10 depicts a design similar to that of the basic subwoofer soundsource as depicted in FIG. 1 and disclosed above.

The submersible sound system 1000 includes a sealed chamber 1010 at aposterior end and a cylindrical bubble source 1020 at an anterior end.The sealed chamber 1010 is composed of a cylindrical housing 1012 towhich a housing end piece 1014 is affixed at a posterior end of thecylindrical housing 1012. The cylindrical bubble source 1020 isconfigured to be filled with gas. The cylindrical bubble source 1020 iscomposed of a cylindrical elastic polyurethane membrane 1022 that isaffixed at an anterior end of the cylindrical housing 1012. Thecylindrical bubble source 1020 also includes an end cap 1024 that issealed at the anterior end of the elastic membrane 1022. The elasticmembrane 1022 may separate the subwoofer driver from the buoyancy forcesof the surrounding water and enable a speaker diaphragm 1036 to beloaded uniformly. In some aspects, the end cap 1024 may be a solidpiece. In some aspects, the end cap 1024 may also include a deformablemembrane.

Disposed within the submersible sound system 1000 is a subwoofer speakersystem 1030. The subwoofer speaker system 1030 is composed of a magnetassembly 1032, a frame, a voice coil (not illustrated), and the speakerdiaphragm 1036. The frame is configured to support the magnet assembly1032 and the speaker diaphragm 1036. The magnet assembly 1032 isdisposed within the sealed chamber 1010 at the posterior end of thesubmersible sound system 1000. The subwoofer speaker system 1030 issupported in the housing 1010 by means of a subwoofer speaker support.The sealed chamber 1010 is maintained in a sealed configuration by meansof the cylindrical housing 1012, the housing end piece 1014, a posteriorend of the subwoofer speaker support, and a posterior surface of thediaphragm 1036.

The speaker diaphragm 1036 is driven by the voice coil in response toreceiving an AC electrical signal. The AC electrical signal may besourced by a control circuit that may control an amplitude and afrequency of the AC electrical signal. The magnetic field developedwithin the voice coil due to the AC electrical signal may cause thevoice coil and the diaphragm 1036, to which it is attached, to moverelative to a static magnetic field produced by the magnet assembly1032. When the diaphragm 1036 is actuated by the voice coil, its motionperturbs the gas disposed within the bubble source 1020. It may beunderstood that the bubble source 1020 may also be maintained in asealed configuration defined by the end cap 1024, the cylindricalelastic membrane 1022, an anterior surface of the subwoofer speakersupport, and an anterior surface of the diaphragm 1036.

The housing 1012 of the underwater subwoofer system 1000 may befabricated from material with a high thermal conductivity to cool airinside subwoofer 1030. In one aspect, the housing 1012 may be fabricatedfrom aluminum 6061 T6. In use, the underwater subwoofer 1000 issurrounded by water. The housing 1012 fabricated with a high temperatureconducting material may cool air inside of the device by heat exchangewith the external water. In addition to the thermally conductive housing1012, the underwater subwoofer system 1000 may include one or more heatsinks 1056 in thermal communication with both the magnet assembly 1032and the housing 1012. In one example, the one or more heat sinks 1056may be composed of copper. In another example, the one or more heatsinks 1056 may be fabricated as heat ducts. If additional thermalconduction is required, the one or more heat sinks 1056 may beimplemented as one or more short heat pipes. The thermal conductivity ofthe one or more heat sinks 1056 may additionally lower temperature,improve temperature balance inside the subwoofer enclosure, and increasethe root means square (RMS) power. Copper has a thermal conductivity ofabout 385 [W/Km]. If a heat sink has a length 5 mm and has across-sectional area of about 0.001 sq. m, and if eight are used withthe magnet system, then a 2 kW excitatory signal is applied to thesubwoofer speaker system, then the subwoofer frame temperature wouldonly rise about 32.5 degrees C. higher than surrounding watertemperature. Such thermal control of the subwoofer speaker system wouldpermit reliable use for a long time. It may be recognized that the oneor more heat sinks 1056 and/or the highly thermal conductive housing1013 may be included into any of the submersible subwoofer systemsdisclosed either above or below.

Underwater Subwoofer System with Band-Pass Resonator

FIG. 11 depicts a band-pass submersible subwoofer sound system 1100. Theband-pass submersible subwoofer sound system 1100 is similar to thevented subwoofer system 400 with the addition of a second Helmhotzresonator disposed anterior to the subwoofer speaker system.

The band-pass submersible sound system 1100 includes a posteriorenclosure 1111 at a posterior end and a cylindrical bubble source 1120at an anterior end. The posterior enclosure 1111 is composed of aposterior portion of a cylindrical housing 1112 to which a housing endpiece 1114 is affixed at a posterior end of the cylindrical housing1112. The cylindrical bubble source 1120 is configured to be filled withgas so that sound can be radiated into the water through the gas-filledcylindrical bubble source 1120. The cylindrical bubble source 1120 iscomposed of a cylindrical elastic polyurethane membrane 1122 that isaffixed at an anterior end of the cylindrical housing 1112. Thecylindrical bubble source 1120 also includes an end cap 1124 that issealed at the anterior end of the elastic membrane 1122. The elasticmembrane 1122 may separate the subwoofer driver from the buoyancy forcesof the surrounding water and enable a speaker diaphragm 1136 to beloaded uniformly. In some aspects, the end cap 1124 may be a solidpiece. In some aspects, the end cap 1124 may also include a deformablemembrane.

Disposed within the band-pass submersible sound system 1100 is asubwoofer speaker system 1130. In some aspects, the subwoofer speakersystem 1130 is disposed in a posterior end of the cylindrical housing1112. The subwoofer speaker system 1130 is composed of a magnetassembly, a frame, a voice coil (not illustrated), and a speakerdiaphragm 1136. The frame is configured to support the magnet assemblyand the speaker diaphragm 1136. The magnet assembly is disposed withinthe posterior enclosure 1111 at the posterior end of the band-passsubmersible sound system 1100. The subwoofer speaker system is supportedin the posterior enclosure 1111 by means of a subwoofer speaker support1138. The posterior enclosure 1111 is thus composed of a posteriorportion of the housing 1112, the housing end piece 1114, a posteriorportion of the subwoofer speaker support 1138, and a posterior surfaceof the speaker diaphragm 1136.

The speaker diaphragm 1136 is driven by the voice coil in response toreceiving an AC electrical signal. The AC electrical signal may besourced by a control circuit that may control an amplitude and afrequency of the AC electrical signal. The magnetic field developedwithin the voice coil due to the AC electrical signal may cause thevoice coil and the diaphragm 1136, to which it is attached, to moverelative to a static magnetic field produced by the magnet assembly.

The band-pass submersible sound system 1100 includes a resonator endwall 1164 at the anterior end of the housing 1112. The portion of thehousing 1112 bounded by the resonator end wall 1164 and the anteriorsurface of the diaphragm 1136 defines a Helmholtz resonator chamber1162, that, together with a resonator throat 1166, forms a Helmholtzresonator. The resonator throat 1166 acoustically and fluidicallycouples the resonator chamber 1162 with the cylindrical bubble source1120. It may be understood that the bubble source 1120 may be maintainedin a sealed configuration defined by the end cap 1124, the cylindricalelastic membrane 1122, and an anterior surface of the resonator end wall1164. When the diaphragm 1136 is actuated by the voice coil, its motionperturbs the gas disposed within the resonator chamber 1162.

The band-pass submersible sound source 1100 may also include a tuningpipe 1150 to vent the sealed compartment 1111 to the Helmholtz resonatorchamber 1162. In some aspects, the tuning pipe 1150 is disposed withinthe subwoofer speaker support 1138 and extends between the sealedcompartment 1111 and the Helmholtz resonator chamber 1162. The tuningpipe 1150 may be configured to permit fluidic communication between thesealed compartment 1111 and the Helmholtz resonator chamber 1162.

FIG. 12 depicts an equivalent electrical circuit 1200 for the band-passsubmersible sound source 1100. The applicable equations are describedabove with reference to FIG. 2. For the Helmholtz resonator,R₀=ω_(r)L_(h)/Q_(h), Q, is the Qfactor of the Helmholtz resonator; ifris the resonance frequency of the Helmholtz resonator;L_(h)=l_(h)ρ_(a)/A_(h); l, is the length of the Helmholtz port and A, isthe area of the Helmholtz port; C_(h)=V_(h)/(γP_(b)); V_(h) is thevolume of the Helmholtz resonator; and r=1.4 is the adiabatic constant.The resonance frequency of the Helmholtz resonators: ω_(r)=1/√{squareroot over (l_(m)ρ_(atm)V_(h)/(γP_(atm)A_(h)))}, where ρ_(atm), P_(atm)are the atmospheric density and pressure of air. The resonance frequencyremains approximately the same at all depth. This makes frequencyresponse of the sound source more stable.

For purposes of simulating the behavior of the band-pass submersiblesubwoofer sound source 1100, simulation parameters for the subwoofer arethe same as those given in Table 1 and the simulation parameters for theenclosure given in Table 4 below. The bandpass resonator differs fromthe sealed and vented variants only by the additional Helmholtz chamberwith the narrow throat that is place anteriorly to the subwoofer speakersystem 1130.

FIG. 13 presents a graph 1300 of sound pressure versus frequency of theband-pass submersible sound system 1100 operating at a depth of 8 m. Theband-pass resonator expands frequency band to range from 12 Hz to 92 Hz.The frequency response does not appear to be sensitive to the waterdepth because Helmholtz resonances do not depend on depth. The bandpassresonator filters all harmonics out of the band and cleans the harmoniccontent.

TABLE 4 Enclosure Diameter of the cylindrical hull, inch 14 Length ofthe motor box, inch 14 Volume of the box, L 35 Length of the bubblemembrane, inch 10 Volume of the bubble, L 25 Area of the membrane, sq. m0.28 Hardness of the membrane, 70 A Thickness of the membrane, mm 3.17Length of the box port pipe, inch 14 Diameter of port, inch 1 Length ofthe Helmholtz chamber, inch 10 Diameter of the Helmholtz throat, inch 3Length of the Helmholtz throat, inch 12 Water depth, m 6

FIG. 14 presents a comparison of the simulated responses of the basicsubwoofer system (300), of the vented subwoofer system (600) and theband-pass subwoofer system (1300). All three underwater subwoofers wereexcited by 2 kW signals and operated at an 8 m depth. All of thesimulations used the same parameters for the subwoofer. The enclosureparameters for the simulations were derived from Table 2 (for the basicdesign), Table 3 (for the vented enclosure) and Table 4 (for theband-pass enclosure). It may be observed that the addition of the tuningpipe shifted the frequency response to lower frequencies and theaddition of the anterior Helmholtz resonator expanded the high frequencyrange of the subwoofer systems. It may be understood that a submersiblesubwoofer sound system may incorporate any one or more of the tuningpipes and/or Helmholtz resonators.

The Helmholtz resonator throat and Helmholtz resonator chamber may formthe Helmholtz resonator with a resonance frequency that is higher thanthe frequency of the bubble resonance. The resonance frequency of theHelmholtz resonator may be seen in FIG. 13 from the first maximum peak(from the right side of the graph in FIG. 13) of the frequency response.As indicated in the graph, this resonance frequency can be a very highfrequency and it can expand the frequency response to 87 Hz. The volumeof Helmholtz resonator works like compliance and the air in the tuningpipe works as inertia. Volume may be calculated relative to theHelmholtz chamber while length and cross area are calculated relative tothe tuning pipe. Equation 15 shows how resonance frequency is related tothe length of the tuning pipe and the cross section area.

$\begin{matrix}{{f_{r} = {\frac{1}{2\; \pi}\sqrt{\frac{{AP}\; \gamma}{\rho_{a}l\; V}}}},} & {{Equation}\mspace{14mu} 15}\end{matrix}$

Underwater Subwoofer System with Band-Pass Resonator and ComputerControl

The operational reliability of the underwater subwoofer may be increasedif it includes a set of sensors providing sensor data that can be usedto control the input power transmitted to drive the subwoofer system.During a typical use of a submersible sound source, the acoustic drivemay be required to have high reliability over a continuous use of hoursand even days. Typical subwoofer speaker systems are designed forcontinuous operation over only a few hours and could readily over-heatif used over a longer duration. Therefore, it is desirable to include acontroller that may control the operation of the subwoofer speakersystem based on data received by the set of sensors in order to preventoverheating. FIG. 15 depicts a band-pass subwoofer sound system 1500similar to the sound system 1100 depicted in FIG. 11 and disclosedabove. It may be recognized that the control system 1580 depicted inFIG. 15 is not limited for use with the band-pass subwoofer sound system1500 but may be used with any of the submersible subwoofer sound systemsdisclosed above, including, without limitation, the basic subwoofersystem 100 (FIG. 1), the vented subwoofer system 400 (FIG. 4), thedual-subwoofer water cooled system 700 (FIG. 7), thedual-resonance/dual-aperture subwoofer system 800 (FIG. 8), and thesubwoofer sound systems containing heat sinks 1000 (FIG. 10). In thecase of the dual-subwoofer sound system 700, a single controller maycontrol each of the subwoofer speaker systems and have separate sensorsassociated with each. Alternatively, each subwoofer speaker system ofthe dual-subwoofer sound system may be controlled by a separatecontroller. In some aspects, each of the separate controllers may beconfigured to communicate with the other controller in order tocoordinate the phasing of the drive signals transmitted to each of therespective subwoofer speaker systems.

As depicted in FIG. 15, the controller may be composed of severalcomponents including, without limitation, a processor, a memory unit indata communication with the processor, a controllable power source orpower amplifier 1584 configured to source a current to drive the voicecoil of the subwoofer speaker system 1530, and an interface to receivesensor input data from a plurality of sensors. In one non-limitingexample, the interface may include an analog to digital converter 1586.

The set of sensors may include any one or more sensors that may providesensor input data to assist the processor in controlling the powertransmitted by the power source 1584. Non-limiting examples of suchsensors may include a sensor of the output current of the power source1584 and a sensor of an output voltage of the power source 1584. In someaspects, one or more of the sensor of the output current and the sensorof the output voltage may be incorporated in the controller 1580. Insome aspects, one or more of the sensor of the output current and thesensor of the output voltage may be incorporated in the subwooferspeaker assembly 1530. In another aspect, one or more of the sensor ofthe output current and the sensor of the output voltage may be separatedevices.

In addition, the set of sensors may include sensors configured tomeasure parameters related to the operation of one or more components ofthe subwoofer speaker assembly 1530. In one example, the set of thesensors may include a temperature sensor 1587 of the voice coil. Thetemperature sensor 1587 of the voice coil may be an infrared (IR)temperature sensor that does not make physical contact with the voicecoil while it moves. In another example, the set of the sensors mayinclude a temperature sensor 1588 configured to measure a temperature ofthe magnet assembly within the subwoofer speaker system 1530. In oneexample, the temperature sensor 1588 may have direct contact with themagnet assembly. In another example, the temperature sensor 1588 maydetect a temperature of the air or gas in contact with the magnetassembly. In another example, the set of sensors may include a sensorconfigured to measure a displacement of the diaphragm during theoperation of the subwoofer speaker system 1530.

It may be recognized that additional sensors may be used to monitoradditional conditions of the submersible subwoofer sound system. Thepresent disclosure is not to be taken to limit such sensors to onlythose explicitly described herein.

The memory component of the controller may include instructions that,when executed by the controller processor, may cause the processor toreceive sensor input data from the sensors and control an output of thepower source 1584 based on the output sensor. The input sensor data mayinclude data from the output current sensor, the output voltage sensor,the temperature sensors 1587, 1588 or any other sensors. It may beunderstood that if the power or temperature conditions of the subwooferexceed a defined safety limit, the processor will cause the power source1584 to decrease its output power, increase the duty cycle of the outputsignal, or shut off the subwoofer speaker system 1530 until theconditions are within the defined safety limit.

The full dynamics of the subwoofer cone can be measured by using thesensors to sense the current and voltage on the speaker. The backelectromotive force (back EMF voltage) can be calculated as the productof the BI-factor or motor force and the voltage of the input signal. Theproduct of the current (Ic) and the BI yields the force applied on thecone. The simple electric current circuit model can be used to determineor calculate any other dynamic parameters based on these two parametersof EMF voltage and current. In general, when the controller causescurrent to be limited, this also limits the force applied on the coneand so that the force is maintained within safe limits. By measuring theback EMF and controlling the power source 1584, the speed of the conemay be limited. Consequently, the amplitude of the cone's excursion canbe limited so that the cone does not exceed its safe limits.

In the subwoofer speaker system 1530, the rate at which the temperatureof the voice coil increase may be a faster rate compared to therespective rate of other part of the subwoofer speaker system 1530. Inparticular, the voice coil can have a temperature up to 250 degreesCelsius. The temperature of the voice coil can reach such maximum levelsfor approximately two to three second. When the underwater subwoofer isused at maximum power, it moves such that its temperature should bemeasured with a suitable infrared remote sensor, such as the MLX90621available from Melexis Technologies. The temperature in the magnetassembly and subwoofer enclosure can be measured by a suitable digitaltemperature sensor such as the ADT7301 available from Analog Devices. Asdiscussed herein, the controller may be programmed to implementtemperature control to prevent overheating, for example. Also, one ormore copper temperature conductors can be provided to cool the magnetassembly and frame of the subwoofer with the surrounded water.

Realized Example of a Submersible Subwoofer System

One example of an experimental submersible subwoofer sound system isdepicted in FIG. 16 in an open configuration 1600 a and in an enclosedconfiguration 1600 b. The realized subwoofer sound system has a modularconstruction and includes sealed (or vented) subwoofer enclosure 1602 atthe posterior end, a Helmholtz resonator 1604 disposed in the middle,and bubble resonator 1606 at the anterior end. The experimental systemincludes multiple internal round plates bolted together with rods. Theinternal structure may slide inside a rigid carbon-fiber pipe 1608. Bychanging the position and number of plates, the realized subwoofer soundsystem can be transformed into any of the considered subwoofer variants:sealed, vented, or band-pass. Experiments conducted using theexperimental system show good agreement with the simulated models.

Clustered Subwoofer System

During testing of the practical underwater subwoofer sound system, itwas determined that, when a distance between two subwoofers is greaterthan 4-5 diameters, the subwoofer acoustic pressure outputs do notcouple but rather directly sum. As a result, the sound pressure outputstogether may have an acoustic power about 6 dB greater than that fromthe individual sound systems. Each submersible sound system will act asif the neighboring sound source does not exist and each sound sourcewill receive the same power from the power source. As a result, thetotal acoustic power of the combined underwater sound system will haveabout four times more acoustical power in the water than the soundsources individually. The efficiency of such system will be twicehigher. The total efficiency of the cluster of N submersible subwoofersound source located at the distance 4-5 times larger than theirdiameter will be N times larger. In order for a cluster of such soundsources to create a spherical wave in the water, the individual soundsources may be mounted at identical distances from each other and havethe same distance from a common phase center defined on a surface of animaginary sphere. Such geometrical structures are known as congruentregular polyhedrals as depicted in FIG. 18. Such polyhedrals mayinclude, without limitations, a tetrahedron 1800 a, an octahedron 1800b, a cube 1800 c, a dodecahedron 1800 d, or an icosahedron 1800 e.

FIG. 17 depicts an illustration of an underwater sound system 1700comprising a cluster of subwoofer sound sources 1720 a-f. The subwoofersound sources may be disposed on a support 1710 which may include anynumber of features configured to maintain the orientation of thesubwoofer sound sources 1720 a-f and permit smooth and stable towing ofthe sound system 1700 at high speed. In one example, the support 1710may include features such as fin-depressors 1733 and a keel 1740. Thesubwoofer sound sources 1720 a-f may be disposed at the vertices of aregular polyhedron. The regular polyhedron can be a cube, for example,as depicted in FIG. 17. Each of the subwoofer sound sources 1720 a-f canradiate sound pressure 182 dB re 1 μPa at 1 m with an efficiency ofabout 0.7% from a 2 kW power amplifier. However, the cluster system 1700may radiate sound pressure at 200 dB re 1 μPa at 1 m and will need 16 kWpower amplifiers. The efficiency of the cluster will be 5.6%. Suchclusters can be combined into array structures and create neededdirectivity patterns.

It may be recognized that the submersible subwoofer sound systems usedin the clustered sound system 1700 may comprise any one of the subwoofersound systems disclosed above including, without limitation, the basicsubwoofer system, the vented subwoofer system, the band-pass subwoofersystem, the water cooled dual subwoofer system, the dual aperture/dualresonance subwoofer system, with or without heat sinks. The subwoofersound systems that together form the cluster may all comprise the sametype of subwoofer sound system, or the sound systems may mix any one ormore types of sound systems. Each of the subwoofer sound systems mayhave its own controller, such as 1580 (see FIG. 15). In some aspects,the individual controllers may be configured to communicate amongthemselves in order to coordinate the amplitude, frequency, and phase oftheir respective subwoofer speaker systems. In another aspect, a singlecontroller may control each of the individual subwoofer speaker systemsand receive sensor input data from each of them.

In cluster or array structure formations as described herein, thedistances between bubble resonators may be so small compared with thewavelength of the wave created in the water such that all the resonatorsmay effectively operate as one big bubble at one phase. Accordingly,systems of the present disclosure such as the clustered sound system1700 advantageously have sound sources that are highly coherent. Anotheradvantage is that the efficiency of the cluster is approximatelyproportional to a number of sources in the cluster. That is, the clustersums the sound pressure from its constituent bubble resonators. Forexample, if the cluster includes a 1 Watt sound source with soundpressure P₀ and another 1 Watt source with the same sound pressure levelP₀ is added to the cluster, the resulting sound pressure will be 2*P₀and the total power will be (2P₀){circumflex over ( )}2 or 4 watts.Thus, doubling the number of sources in a cluster will provide fourtimes more energy from the same electric power. As such, providing acluster so that the sources work together in the cluster is moreefficient than efficiency of one source alone.

Having shown and described various aspects of the present disclosure,further adaptations of the methods and systems described herein may beaccomplished by appropriate modifications by one of ordinary skill inthe art without departing from the scope of the present disclosure.Several of such potential modifications have been mentioned, and otherswill be apparent to those skilled in the art. For instance, theexamples, aspects, geometrics, materials, dimensions, ratios, steps, andthe like discussed above are illustrative and are not required.Accordingly, the scope of the present disclosure should be considered interms of the following claims and is understood not to be limited to thedetails of structure and operation shown and described in thespecification and drawings.

While various details have been set forth in the foregoing description,it will be appreciated that the various aspects of the system and methodfor using sleep enhancement during sleep may be practiced without thesespecific details. One skilled in the art will recognize that the hereindescribed components (e.g., operations), devices, objects, and thediscussion accompanying them are used as examples for the sake ofconceptual clarity and that various configuration modifications arecontemplated. Consequently, as used herein, the specific exemplars setforth and the accompanying discussion are intended to be representativeof their more general classes. In general, use of any specific exemplaris intended to be representative of its class, and the non-inclusion ofspecific components (e.g., operations), devices, and objects should notbe taken limiting.

Further, while several forms have been illustrated and described, it isnot the intention of the applicant to restrict or limit the scope of theappended claims to such detail. Numerous modifications, variations,changes, substitutions, combinations, and equivalents to those forms maybe implemented and will occur to those skilled in the art withoutdeparting from the scope of the present disclosure. Moreover, thestructure of each element associated with the described forms can bealternatively described as a means for providing the function performedby the element. Also, where materials are disclosed for certaincomponents, other materials may be used. It is therefore to beunderstood that the foregoing description and the appended claims areintended to cover all such modifications, combinations, and variationsas falling within the scope of the disclosed forms. The appended claimsare intended to cover all such modifications, variations, changes,substitutions, modifications, and equivalents.

For conciseness and clarity of disclosure, selected aspects of theforegoing disclosure have been shown in block diagram form rather thanin detail. Some portions of the detailed descriptions provided hereinmay be presented in terms of instructions that operate on data that isstored in a computer memory. Such descriptions and representations areused by those skilled in the art to describe and convey the substance oftheir work to others skilled in the art. In general, an algorithm refersto a self-consistent sequence of steps leading to a desired result,where a “step” refers to a manipulation of physical quantities whichmay, though need not necessarily, take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It is common usage to refer tothese signals as bits, values, elements, symbols, characters, terms,numbers, or the like. These and similar terms may be associated with theappropriate physical quantities and are merely convenient labels appliedto these quantities.

Unless specifically stated otherwise as apparent from the foregoingdisclosure, it is appreciated that, throughout the foregoing disclosure,discussions using terms such as “processing” or “computing” or“calculating” or “determining” or “displaying” or the like, refer to theaction and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

In a general sense, those skilled in the art will recognize that thevarious aspects described herein which can be implemented, individuallyand/or collectively, by a wide range of hardware, software, firmware, orany combination thereof can be viewed as being composed of various typesof “electrical circuitry.” Consequently, as used herein “electricalcircuitry” includes, but is not limited to, electrical circuitry havingat least one discrete electrical circuit, electrical circuitry having atleast one integrated circuit, electrical circuitry having at least oneapplication specific integrated circuit, electrical circuitry forming ageneral purpose computing device configured by a computer program (e.g.,a general purpose computer configured by a computer program which atleast partially carries out processes and/or devices described herein,or a microprocessor configured by a computer program which at leastpartially carries out processes and/or devices described herein),electrical circuitry forming a memory device (e.g., forms of randomaccess memory), and/or electrical circuitry forming a communicationsdevice (e.g., a modem, communications switch, or optical-electricalequipment). Those having skill in the art will recognize that thesubject matter described herein may be implemented in an analog ordigital fashion or some combination thereof.

The foregoing detailed description has set forth various forms of thedevices and/or processes via the use of block diagrams, flowcharts,and/or examples. Insofar as such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof. In one form, severalportions of the subject matter described herein may be implemented viaan application specific integrated circuits (ASIC), a field programmablegate array (FPGA), a digital signal processor (DSP), or other integratedformats. However, those skilled in the art will recognize that someaspects of the forms disclosed herein, in whole or in part, can beequivalently implemented in integrated circuits, as one or more computerprograms running on one or more computers (e.g., as one or more programsrunning on one or more computer systems), as one or more programsrunning on one or more processors (e.g., as one or more programs runningon one or more microprocessors), as firmware, or as virtually anycombination thereof, and that designing the circuitry and/or writing thecode for the software and or firmware would be well within the skill ofone of skill in the art in light of this disclosure. In addition, thoseskilled in the art will appreciate that the mechanisms of the subjectmatter described herein are capable of being distributed as a programproduct in a variety of forms, and that an illustrative form of thesubject matter described herein applies regardless of the particulartype of signal bearing medium used to actually carry out thedistribution. Examples of a signal bearing medium include, but are notlimited to, the following: a recordable type medium such as a floppydisk, a hard disk drive, a Compact Disc (CD), a Digital Video Disk(DVD), a digital tape, a computer memory, etc.; and a transmission typemedium such as a digital and/or an analog communication medium (e.g., afiber optic cable, a waveguide, a wired communications link, a wirelesscommunication link (e.g., transmitter, receiver, transmission logic,reception logic, etc.), etc.).

In some instances, one or more elements may be described using theexpression “coupled” and “connected” along with their derivatives. Itshould be understood that these terms are not intended as synonyms foreach other. For example, some aspects may be described using the term“connected” to indicate that two or more elements are in direct physicalor electrical contact with each other. In another example, some aspectsmay be described using the term “coupled” to indicate that two or moreelements are in direct physical or electrical contact. The term“coupled,” however, also may mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other. It is to be understood that depicted architectures ofdifferent components contained within, or connected with, differentother components are merely examples, and that in fact many otherarchitectures may be implemented which achieve the same functionality.In a conceptual sense, any arrangement of components to achieve the samefunctionality is effectively “associated” such that the desiredfunctionality is achieved. Hence, any two components herein combined toachieve a particular functionality can be seen as “associated with” eachother such that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated also can be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated also can be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents, and/or wirelessly interactable, and/or wirelesslyinteracting components, and/or logically interacting, and/or logicallyinteractable components.

In other instances, one or more components may be referred to herein as“configured to,” “configurable to,” “operable/operative to,”“adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Thoseskilled in the art will recognize that “configured to” can generallyencompass active-state components and/or inactive-state componentsand/or standby-state components, unless context requires otherwise.

While particular aspects of the present disclosure have been shown anddescribed, it will be apparent to those skilled in the art that, basedupon the teachings herein, changes and modifications may be made withoutdeparting from the subject matter described herein and its broaderaspects and, therefore, the appended claims are to encompass withintheir scope all such changes and modifications as are within the truescope of the subject matter described herein. It will be understood bythose within the art that, in general, terms used herein, and especiallyin the appended claims (e.g., bodies of the appended claims) aregenerally intended as “open” terms (e.g., the term “including” should beinterpreted as “including but not limited to,” the term “having” shouldbe interpreted as “having at least,” the term “includes” should beinterpreted as “includes but is not limited to,” etc.). It will befurther understood by those within the art that if a specific number ofan introduced claim recitation is intended, such an intent will beexplicitly recited in the claim, and in the absence of such recitationno such intent is present. For example, as an aid to understanding, thefollowing appended claims may contain usage of the introductory phrases“at least one” and “one or more” to introduce claim recitations.However, the use of such phrases should not be construed to imply thatthe introduction of a claim recitation by the indefinite articles “a” or“an” limits any particular claim containing such introduced claimrecitation to claims containing only one such recitation, even when thesame claim includes the introductory phrases “one or more” or “at leastone” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an”should typically be interpreted to mean “at least one” or “one ormore”); the same holds true for the use of definite articles used tointroduce claim recitations.

In addition, even if a specific number of an introduced claim recitationis explicitly recited, those skilled in the art will recognize that suchrecitation should typically be interpreted to mean at least the recitednumber (e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that typically a disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms unless context dictates otherwise. For example, the phrase “Aor B” will be typically understood to include the possibilities of “A”or “B” or “A and B.”

With respect to the appended claims, those skilled in the art willappreciate that recited operations therein may generally be performed inany order. Also, although various operational flows are presented in asequence(s), it should be understood that the various operations may beperformed in other orders than those which are illustrated, or may beperformed concurrently. Examples of such alternate orderings may includeoverlapping, interleaved, interrupted, reordered, incremental,preparatory, supplemental, simultaneous, reverse, or other variantorderings, unless context dictates otherwise. Furthermore, terms like“responsive to,” “related to,” or other past-tense adjectives aregenerally not intended to exclude such variants, unless context dictatesotherwise.

It is worthy to note that any reference to “one aspect,” “an aspect,”“one form,” or “a form” means that a particular feature, structure, orcharacteristic described in connection with the aspect is included in atleast one aspect. Thus, appearances of the phrases “in one aspect,” “inan aspect,” “in one form,” or “in an form” in various places throughoutthe specification are not necessarily all referring to the same aspect.Furthermore, the particular features, structures or characteristics maybe combined in any suitable manner in one or more aspects.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations are not expressly set forth herein for sakeof clarity.

In certain cases, use of a system or method may occur in a territoryeven if components are located outside the territory. For example, in adistributed computing context, use of a distributed computing system mayoccur in a territory even though parts of the system may be locatedoutside of the territory (e.g., relay, server, processor, signal-bearingmedium, transmitting computer, receiving computer, etc. located outsidethe territory).

A sale of a system or method may likewise occur in a territory even ifcomponents of the system or method are located and/or used outside theterritory. Further, implementation of at least part of a system forperforming a method in one territory does not preclude use of the systemin another territory.

All of the above-mentioned U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications, non-patent publications referred to in this specificationand/or listed in any Application Data Sheet, or any other disclosurematerial are incorporated herein by reference, to the extent notinconsistent herewith. As such, and to the extent necessary, thedisclosure as explicitly set forth herein supersedes any conflictingmaterial incorporated herein by reference. Any material, or portionthereof, that is said to be incorporated by reference herein, but whichconflicts with existing definitions, statements, or other disclosurematerial set forth herein will only be incorporated to the extent thatno conflict arises between that incorporated material and the existingdisclosure material.

In summary, numerous benefits have been described which result fromemploying the concepts described herein. The foregoing description ofthe one or more forms has been presented for purposes of illustrationand description. It is not intended to be exhaustive or limiting to theprecise form disclosed. Modifications or variations are possible inlight of the above teachings. The one or more forms were chosen anddescribed in order to illustrate principles and practical application tothereby enable one of ordinary skill in the art to utilize the variousforms and with various modifications as are suited to the particular usecontemplated. It is intended that the claims submitted herewith definethe overall scope.

Various embodiments are described in the following numbered examples:

Example 1. A submersible sound system comprising: a housing; a housingend piece in mechanical communication with a posterior end of thehousing; an elastic membrane in mechanical communication with ananterior end of the housing; an end cap in mechanical communication withthe elastic membrane; a subwoofer speaker system disposed within thehousing. The subwoofer speaker system comprises: a magnet assemblydisposed within the posterior end of the housing; a frame in mechanicalcommunication with the magnet assembly; a voice coil; a diaphragm inmechanical communication with the frame and configured to be driven bythe voice coil; a subwoofer speaker support in mechanical communicationwith the frame; and an interior portion of the housing, and wherein ananterior surface of the subwoofer speaker support, an anterior surfaceof the diaphragm, the anterior end of the housing, the elastic membrane,and the end cap together define a sealed cylindrical bubble soundsource.

Example 2. The submersible sound system of Example 1, wherein thehousing, the housing end piece, and a posterior surface of the subwooferspeaker support together form a sealed enclosure in the housing.

Example 3. The submersible sound system of Examples 1 or 2, comprising atuning pipe disposed within the subwoofer speaker support, extendingbetween the sealed enclosure and the cylindrical bubble sound source,and configured to permit fluidic communication between the sealedenclosure and the cylindrical bubble sound source.

Example 4. The submersible sound system of Example 3, wherein the tuningpipe and the sealed enclosure together comprise a Helmholtz resonator.

Example 5. The submersible sound system of any of Examples 1-4,comprising a second subwoofer speaker system disposed within thehousing. The second subwoofer speaker system comprises a second magnetassembly disposed within the posterior end of the housing; a secondframe in mechanical communication with the second magnet assembly; asecond voice coil; a second diaphragm in mechanical communication withthe second frame and configured to be driven by the second voice coil;and a second subwoofer speaker support in mechanical communication withthe second frame and an interior portion of the posterior end of thehousing, wherein the second subwoofer speaker system is disposed in anopposing direction to the subwoofer speaker system; and a sealed channelconfigured to permit fluidic communication between a posterior side ofthe frame and an anterior side of the second frame, wherein thediaphragm is a first diaphragm and the first diaphragm is configured tooperate in opposition to the second diaphragm.

Example 6. The submersible sound system of any of Examples 1-5,comprising a second cylindrical bubble sound source comprising a secondelastic membrane in mechanical communication with the posterior end ofthe housing at a first end of the second elastic membrane and inmechanical communication with the housing end piece at a second end ofthe second elastic membrane, wherein the second elastic membrane, thehousing, the housing end piece, and a posterior surface of the subwooferspeaker support together form a sealed enclosure.

Example 7. The submersible sound system of any of Examples 1-6, furthercomprising one or more heat sinks in thermal communication with themagnet assembly and the housing.

Example 8. The submersible sound system of any of Examples 7, whereinthe one or more heat sinks are configured to be positioned in proximityto water to cool the water.

Example 9. The submersible sound system of any of Examples 1-8, furthercomprising a gas disposed therein.

Example 10. The submersible sound system of any of Examples 1-9, whereinthe end cap comprises an elastic portion.

Example 11. The submersible sound system of any of Examples 1-10,comprising a control system. The control system comprises a processor; amemory unit in data communication with the processor; a controllablepower source in electrical communication with the voice coil; and aninterface configured to receive sensor input data from the subwooferspeaker system; wherein the memory unit stores instructions that, whenexecuted by the processor, cause the processor to: receive the sensorinput data from the subwoofer speaker system; and control the powersource based on the received sensor input data.

Example 12. The submersible sound system of any of Examples 11, whereinthe subwoofer speaker system comprises a first temperature sensor of afirst temperature of fluid surrounding the magnet assembly and a secondtemperature sensor of a second temperature of the voice coil.

Example 13. The submersible sound system of Example 12, wherein thesecond temperature sensor is an IR temperature sensor.

Example 14. The submersible sound system of any of Examples 12-13,wherein the sensor input data are received from one or more of the firsttemperature sensor and the second temperature sensor.

Example 15. The submersible sound system of any of Examples 11-15,comprising a sensor of an output current of the power source; and asensor of an output voltage of the power source, wherein the memory unitstores instructions that, when executed by the processor, further causethe processor to: receive current data from the sensor of the outputcurrent; receive voltage data from the sensor of the output voltage; andcontrol the power source based on the received current data and thereceived voltage data.

Example 16. A submersible sound system comprising: a housing; a housingend piece in mechanical communication with a posterior end of thehousing; an elastic membrane in mechanical communication with ananterior end of the housing; an end cap in mechanical communication withthe elastic membrane; a resonator end wall in mechanical communicationwith the anterior end of the housing; a resonator throat disposed withinthe resonator end wall; and a subwoofer speaker system disposed withinthe housing. The subwoofer speaker system comprises: a magnet assemblydisposed within the posterior end of the housing; a frame in mechanicalcommunication with the magnet assembly; a voice coil; a diaphragm inmechanical communication with the frame and configured to be driven bythe voice coil; a subwoofer speaker support in mechanical communicationwith the frame and an interior portion of the housing; and a tuning pipedisposed within the subwoofer speaker support; wherein the housing, thehousing end piece, and a posterior surface of the subwoofer speakersupport together form a posterior enclosure, wherein an anterior surfaceof the resonator end wall, the anterior end of the housing, the elasticmembrane, and the end cap together define a sealed cylindrical bubblesound source, wherein the anterior surface of the diaphragm, an anteriorsurface of the subwoofer speaker support, an anterior portion of thehousing, the resonator end wall, and the resonator throat togetherdefine a Helmholtz resonator, wherein the resonator throat is configuredto permit fluidic communication between the Helmholtz resonator and thecylindrical bubble sound source, and wherein the tuning pipe extendsbetween the posterior enclosure and the Helmholtz resonator and isconfigured to permit fluidic communication between the posteriorenclosure and the Helmholtz resonator.

Example 17. The submersible sound system of Example 16, comprising acontrol system. The control system comprises: a processor; a memory unitin data communication with the processor; a controllable power source inelectrical communication with the voice coil; and an interfaceconfigured to receive sensor input data from the subwoofer speakersystem; wherein the memory unit stores instructions that, when executedby the processor, cause the processor to: receive the sensor input datafrom the subwoofer speaker system; an control the power source based onthe received sensor input data, an output voltage of the power source,and an output current of the power source.

Example 18. An underwater sound system comprising: a sound systemsupport having a plurality of vertices and a plurality of sound sources.The plurality of vertices form the vertices of a regular polyhedron.Each of the plurality of sound sources comprise: a housing; a housingend piece in mechanical communication with a posterior end of thehousing; an elastic membrane in mechanical communication with theanterior end of the housing; an end cap in mechanical communication withthe elastic membrane; and a subwoofer speaker system disposed within thehousing. The subwoofer speaker system comprises a magnet assemblydisposed within the posterior end of the housing; a frame in mechanicalcommunication with the magnet assembly; a voice coil; a diaphragm inmechanical communication with the frame and configured to be driven bythe voice coil; and a subwoofer speaker support in mechanicalcommunication with the frame and an interior portion of the housing. Ananterior surface of the subwoofer speaker support, an anterior surfaceof the diaphragm, the anterior end of the housing, the elastic membrane,and the end cap together define a sealed cylindrical bubble soundsource. Each one of the plurality of sound sources is affixed to eachone of the plurality of sound system support vertices.

Example 19. The underwater sound system of Example 18, wherein the soundsystem support further comprises one or more suppressor fins and keels.

Example 20. The underwater sound system of claim 18, wherein the regularpolyhedron comprises one of a tetrahedron, a cube, an octahedron, adodecahedron, and an icosahedron.

1-10. (canceled)
 11. The underwater sound system of claim 18, whereineach of the plurality of sound sources further comprises: a controlsystem comprising: a processor; a memory unit in data communication withthe processor; a controllable power source in electrical communicationwith the voice coil of the sound source; and an interface configured toreceive sensor input data from the subwoofer speaker system of the soundsource; wherein the memory unit stores instructions that, when executedby the processor, cause the processor to: receive the sensor input datafrom the subwoofer speaker system; and control the power source based onthe received sensor input data.
 12. The underwater sound system of claim11, wherein the subwoofer speaker system of each of the plurality ofsound sources comprises a first temperature sensor of a firsttemperature of fluid surrounding the magnet assembly and a secondtemperature sensor of a second temperature of the voice coil.
 13. Theunderwater sound system of claim 12, wherein the second temperaturesensor is an IR temperature sensor.
 14. The underwater sound system ofclaim 12, wherein the sensor input data are received from one or more ofthe first temperature sensor and the second temperature sensor.
 15. Theunderwater sound system of claim 11, wherein each of the plurality ofsound sources further comprises: a sensor of an output current of thepower source of the sound source; and a sensor of an output voltage ofthe power source of the sound source, wherein the memory unit storesinstructions that, when executed by the processor, further cause theprocessor to: receive current data from the sensor of the outputcurrent; receive voltage data from the sensor of the output voltage; andcontrol the power source based on the received current data and thereceived voltage data. 16-17. (canceled)
 18. An underwater sound systemcomprising: a sound system support having a plurality of vertices,wherein the plurality of vertices form the vertices of a regularpolyhedron; and a plurality of sound sources, wherein each of theplurality of sound sources comprise: a housing; a housing end piece inmechanical communication with a posterior end of the housing; an elasticmembrane in mechanical communication with the anterior end of thehousing; an end cap in mechanical communication with the elasticmembrane; a subwoofer speaker system disposed within the housing, thesubwoofer speaker system comprising: a magnet assembly disposed withinthe posterior end of the housing; a frame in mechanical communicationwith the magnet assembly; a voice coil; a diaphragm in mechanicalcommunication with the frame and configured to be driven by the voicecoil; and a subwoofer speaker support in mechanical communication withthe frame and an interior portion of the housing; wherein an anteriorsurface of the subwoofer speaker support, an anterior surface of thediaphragm, the anterior end of the housing, the elastic membrane, andthe end cap together define a sealed cylindrical bubble sound source,wherein each one of the plurality of sound sources is affixed to eachone of the plurality of sound system support vertices.
 19. Theunderwater sound system of claim 18, wherein the sound system supportfurther comprises one or more suppressor fins and keels.
 20. Theunderwater sound system of claim 18, wherein the regular polyhedroncomprises one of a tetrahedron, a cube, an octahedron, a dodecahedron,and an icosahedron.
 21. The underwater sound system of claim 11, whereineach control system of the plurality of sound sources is configured tocommunicate with at least one other control system of the plurality ofsound sources.
 22. The underwater sound system of claim 21, wherein eachcontrol system is configured to coordinate an amplitude, a frequency, ora phase of its subwoofer speaker system with a subwoofer speaker systemcontrolled by the at least one other control system.
 23. The underwatersound system of claim 18, further comprising: a control systemcomprising: a processor; a memory unit in data communication with theprocessor; a controllable power source in electrical communication witheach of the voice coils of the plurality of sound source; and aninterface configured to receive sensor input data from each of thesubwoofer speaker systems of the plurality of sound sources, wherein thememory unit stores instructions that, when executed by the processor,cause the processor to: receive the sensor input data from the subwooferspeaker system; and control the power source based on the receivedsensor input data.